Head design with low coefficient of thermal expansion insert layer

ABSTRACT

A magnetic read/write head is produced with an insert layer between the substrate and the magnetic transducer. The insert layer has a lower coefficient of thermal expansion than the substrate, which reduces the temperature pole tip recession (T-PTR) of the head because the insert layer is an intervening layer between the substrate and magnetic transducer. The insert layer is produced by plating, e.g., an Invar layer over the substrate prior to fabricating the magnetic transducer. The Invar layer is annealed and the structure planarized prior to depositing a non-magnetic gap layer followed by the fabrication of the magnetic transducer.

FIELD OF THE INVENTION

The present invention relates to magnetic read/write heads, and inparticular to magnetic read/write heads with reduced thermal pole-tipprotrusion.

BACKGROUND

Magnetic read/write heads, such as those used in hard disk drives,include a magnetic transducer with a write element and a read elementdisposed on a substrate. The write element is an inductive transducer,which includes electrically conductive coil windings that are encircledby a magnetic core. The magnetic core includes a first and second poletips with a non-magnetic gap disposed between the tips. When electricalcurrent flows through the coil a magnetic field is induced across thenon-magnetic gap at the pole tips to write on the magnetic media, i.e.,the hard disk, which is near the pole tips.

The read element is typically formed between the write element and thesubstrate and typically includes first and second shield layers with amagnetoresistive (MR) sensor formed therebetween. Magnetic flux from thesurface of the magnetic media causes the rotation of a magnetizationvector in the MR sensor, which causes a change in resistivity. Thus, thepresence of magnetic flux at the surface of the magnetic media may bedetected by measuring the change in resistivity of the MR sensor.

The read/write elements are located at the trailing end of the substratealong the air bearing surface. In operation, the head flies above thespinning magnetic disk so that the read/write elements are positioned inclose proximity to the magnetic recording media. Ideally, the read/writeelements are close enough to the magnetic media to produce a large datadensity, however, the distance should be great enough that contactbetween the read/write elements and the magnetic media does not occur.

Because the read/write elements are fabricated from materials differentfrom that of the substrate, the read/write elements and the substratetypically have differing coefficients of thermal expansion (CTE).Generally, the read/write elements include metallic layers causing theread/write elements to have a greater CTE than the substrate. Duringoperation, as the read/write head flies above the spinning magneticmedia, the read/write head is subjected to increased temperatures. Theincreased temperatures and the greater CTE of the read/write elementscauses the read/write elements to protrude closer to the magnetic mediathan the substrate, which is known as thermal pole tip protrusion(T-PTR). Thus, T-PTR requires an increase in the fly height of theread/write head in order to avoid contact between the read/writeelements and the magnetic media during high operating temperatures.

Accordingly, it is desirable to reduce the amount of T-PTR in aread/write head so as to reduce variation in the distance between theread/write elements and the magnetic media during operation, whichpermits a decrease in the required fly height of the head.

SUMMARY

A magnetic read/write head, in accordance with an embodiment of thepresent invention, is produced with an insert layer that has a lower CTEthan the substrate and that is positioned between the substrate and themagnetic transducer. With the magnetic transducer deposited over the lowCTE insert layer, the expansion of the magnetic transducer is restrictedduring operation thereby decreasing the T-PTR of the head. The insertlayer is produced by plating and annealing, e.g., an Invar NiFe layerover the substrate prior to fabricating the magnetic transducer.

In one aspect of the present invention, a magnetic read/write headincludes a substrate and a magnetic transducer that is coupled to thesubstrate. The magnetic transducer has a coefficient of thermalexpansion that is greater than the coefficient of thermal expansion ofthe substrate. The head also includes a conductive layer that is coupledbetween the substrate and the magnetic transducer. The conductive layerhas a coefficient of thermal expansion that is less than the coefficientof thermal expansion of the substrate. In addition, the head includes anon-magnetic layer that is coupled between the conductive layer and themagnetic transducer.

In another aspect of the present invention, a method of forming amagnetic read/write head includes providing a substrate and plating aNiFe layer over the substrate. The NiFe layer is annealed and anon-magnetic layer is deposited over the NiFe layer. A magnetictransducer is then formed over the non-magnetic layer.

In yet another aspect of the present invention, a method of forming amagnetic read/write head includes providing a substrate, plating aconductive layer over the substrate, and annealing the conductive layer,wherein the annealed conductive layer has a coefficient of thermalexpansion that is less than the coefficient of thermal expansion of thesubstrate. The method further includes depositing a non-magnetic layerover the conductive layer and fabricating a magnetic transducer over thenon-magnetic layer, wherein the magnetic transducer has a coefficient ofthermal expansion that is greater than the coefficient of thermalexpansion of the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view, perpendicular to the air bearingsurface, of a portion of a magnetic read/write head, in accordance withan embodiment of the present invention.

FIGS. 2A and 2B illustrate the effect of T-PTR on a magnet head, inaccordance with an embodiment of the present invention, where FIG. 2Aillustrates the head prior to heating and FIG. 2B illustrates the headafter heating.

FIGS. 3A and 3B illustrate the effect of T-PTR on a conventional head,where FIG. 3A illustrates the head prior to heating and FIG. 3Billustrates the head after heating.

FIG. 4 illustrates a graph modeling the T-PTR for two conventional headsand a head, in accordance with an embodiment of the present invention.

FIG. 5 is a flow chart of the process of fabricating a magneticread/write head in accordance with an embodiment of the presentinvention.

FIGS. 6A-6E schematically illustrates the fabrication process for amagnetic read/write head in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION

FIG. 1 is a cross-sectional view, perpendicular to the air bearingsurface (ABS), of a portion of a magnetic read/write head 100 inaccordance with an embodiment of the present invention. The magnetichead 100 includes an insert layer 110 that has a lower coefficient ofthermal expansion (CTE) than that of the substrate, which advantageouslyreduces temperature induced pole tip recession during operation of thehead.

As illustrated in FIG. 1, the head 100 includes a slider substrate 102,which is manufactured from materials, such as AlTiC, TiC, Si, SiC Al₂O₃or other similar materials or composites formed from combinations ofthese materials. An undercoat layer 104, e.g., of alumina, is depositedover the substrate 102. Over the undercoat layer 104 is deposited theinsert layer 110. The insert layer 110 is an alloy of nickel (Ni) andiron (Fe), which is sometimes referred to Invar, which advantageouslyhas a low CTE. A non-magnetic spacer 112 is deposited over the insertlayer 110. The non-magnetic spacer 112 is used to break the magneticcoupling of the insert layer 110 from the magnetic transducer 120.

A magnetic transducer 120 is fabricated over the non-magnetic spacer 112in any desired fashion. Magnetic transducers and their fabrication arewell known, and accordingly, magnetic transducer 120 is shown merely forillustrative purposes. The present invention is not limited to anyparticular type of magnetic transducer. Thus, any desired magnetictransducer may be fabricated over the non-magnetic spacer layer 112.

As illustrated in FIG. 1, the magnetic transducer 120 may include, e.g.,a read portion 130 with a first shield layer 132, an insulator layer 134in which is disposed a sensor element (not shown) and a second shieldlayer 136.

The write portion 140 of the magnetic transducer 120 may include a firstpole piece 142 and a second pole piece 144 that are separated at the ABSby a write gap layer 150 and a third pole piece 146. The third polepiece 146 connects the first pole piece 142 and the second pole piece144 at the back gap (BG). The third pole piece 146 is formed on eitherside at the write gap layer 150 at the ABS. The write portion 140 alsoincludes two coil layers 152 and 154, which surround the write gap layer150 and which are covered with resist 153 and 155. It should beunderstood that the write coil may be in a single layer if desired.

The magnetic read/write head 100 has a reduced amount of T-PTR, relativeto conventional heads, because the insert layer 110 has a lower CTE thanthe substrate 102 and the insert layer 110 is disposed between thesubstrate 102 and the magnetic transducer 120. During operation, theinsert layer 110 will expand less than the substrate 102. Because themagnetic transducer 120 is formed on the insert layer 110, as opposed tothe substrate 102, the insert layer 110 will restrict the expansion ofthe magnetic transducer 120.

FIGS. 2A and 2B illustrate the effect of T-PTR on a magnet head 100,where an insert layer 110 is disposed between the substrate 102 and themagnetic transducer 120. FIG. 2A illustrates the head 100 prior toheating and FIG. 2B illustrates the head 100 after heating, with theexpansion of the substrate 102 and the magnetic transducer 120 greatlyexaggerated. As can be seen in FIG. 2B, the insert layer 110, whichexpands less than the substrate 102, resists the expansion of themagnetic transducer 120. The insert layer 110 limits the expansion ofthe magnetic transducer 120 to an amount that is closer to the expansionof the substrate 102. Accordingly, the magnetic transducer 120 haslittle protrusion, illustrated as T-PTR₁₀₀, beyond the substrate 102,resulting in a reduced amount of T-PTR relative to conventional heads.

FIGS. 3A and 3B illustrate the effect of T-PTR on a conventional head200, where a magnetic transducer 204 is coupled to the substrate 202without an intervening Invar insert layer. FIG. 3A illustrates the head200 prior to heating and FIG. 3B illustrates the head 200 after heatingwith the expansion of the substrate 202 and the magnetic transducer 204greatly exaggerated. As can be seen in FIG. 3B, in the conventional head200, the magnetic transducer 204 expands more than the substrate 202when heated, but the expansion of the magnetic transducer 204 is limitedby the substrate 202. Accordingly, the magnetic transducer 204 protrudescloser to the underlying magnetic media (not shown) than the substrate202, resulting in a large amount of T-PTR.

FIG. 4 illustrates a graph illustrating the modeling results of theT-PTR (in nm at 30° C.) as a function of distance from the undercoat,i.e., layer 104 in FIG. 1, for two conventional heads and a head with anInvar insert, in accordance with the present invention. As can be seen,the head with the Invar insert has a substantial reduction in the T-PTRcompared to conventional heads. In fact, the maximum T-PTR for a head inaccordance with the present invention is 0.55 nm compared to 1.1 nm forthe head labeled Conv2.

FIG. 5 is a flow chart of the process of fabricating a magneticread/write head in accordance with an embodiment of the presentinvention. FIGS. 6A-6E schematically illustrates the fabricationprocess. It should be understood that FIG. 5 and FIGS. 6A-6E, describethe fabrication of a single head for the sake of simplicity and that thefabrication is performed at the wafer level, where multiple heads arefabricated simultaneously and then separated.

As described in FIG. 5, first a substrate with an undercoating isprovided (block 302). The substrate may be, e.g., a manufactured fromAlTiC, TiC, Si, SiC Al₂O₃ or other similar materials or compositesformed from combinations of these materials. By way of example, a AlTiCsubstrate with a CTE of approximately 6×10⁻⁶/° C. may be used. Theundercoating may be, e.g., 0.7 μm to 1.0 μm of alumina. A seed layer isthen deposited over the undercoating (block 304). The seed layer may be,e.g., 32/68 or 45/55 of nickel and iron, and may be, e.g., sputterdeposited to a thickness of, e.g., 300-2000 Å. Other seed layers,including non-magnetic but conductive seed layers, may be used ifdesired, such as V or NiCr.

The Invar insert layer is then frame plated over the seed layer (block306). The Invar insert layer is produced with 34 to 38 percent Ni and 62to 66 percent Fe to a thickness of between approximately 1.0 μm to 5.0μm. In one embodiment, Invar insert layer is Ni₃₆Fe₆₄ and isapproximately 4.0 μm. In another embodiment, the insert may be producedwith plated CoNiFe, where Co is 0.1 to 5.0 percent, Ni is 35 to 36percent, and Fe is 62 to 64 percent. FIG. 6A shows an illustrative crosssection of the frame plated Invar insert layer 410 deposited over theseed layer 406, undercoating 404 and the substrate 402. The plating maskfor the Invar insert layer may have approximately the same size and/orshape, or larger, as the first shield in the magnetic transducer. Ifdesired, alignment marks may be produced with the frame plating at thisstep to be used in later fabrication of the magnetic transducer.

The plating field and the seed layer underlying the plating field arethen removed by, e.g., wet etching, (block 308), resulting in thestructure shown in FIG. 6B. After the plating field and seed layerremoval, the Invar insert layer and gaps are covered with an overcoatlayer (block 310). The overcoat layer may be the same material as usedfor the undercoating, i.e. alumina. FIG. 6C illustrates the resultingstructure with the overcoat layer 412 deposited over the Invar insertlayer 410. The overcoat layer 412 should be deposited to a thicknessthat is greater than the Invar insert layer 410, e.g., 4.0 μm to 5.0 μm,so that the structure may be planarized later.

With the Invar insert layer 410 covered with the overcoat layer 412, thestructure is annealed at a temperature greater than 450° C., e.g.,between approximately 450° C. and 800° C., e.g., at 490° C., for betweenapproximately 1 and 10 hours, e.g., for 2 hours, with a slow temperatureramp (block 312). The annealing of the Invar insert layer 410advantageously produces a phase transition in the material that reducesthe CTE to, e.g., 4.5×10⁻⁶/° C.

The structure is then planarized, e.g., by chemical mechanicalpolishing, to the desired final thickness of the Invar insert layer,e.g., 4 μm (block 314). FIG. 6D illustrates the structure afterplanarizing.

A non-magnetic spacer layer is deposited over the Invar insert layer(block 316). The non-magnetic spacer layer may be, e.g., a layer of Ta,that is sputter deposited to a thickness of approximately 0.1 μm to 1.0μm, e.g., 0.25 μm. If desired, other non-magnetic low expansionmaterials, such as AlO₂, may be used, however, the use of Ta isdesirable as it provides good heat dissipation. FIG. 6E illustrates thestructure with the non-magnetic spacer layer 414 over the Invar insertlayer 410 and the remaining overcoating layer 412. The deposition of thenon-magnetic spacer layer may be followed with any desired conventionalmagnetic transducer fabrication process (block 318).

Although the present invention is illustrated in connection withspecific embodiments for instructional purposes, the present inventionis not limited thereto. Various adaptations and modifications may bemade without departing from the scope of the invention. For example,additional layers, such as adhesion layers, may be used with the presentinvention. Moreover, the present invention is not limited to anyparticular magnetic transducer. Therefore, the spirit and scope of theappended claims should not be limited to the foregoing description.

1. A magnetic read/write head comprising: a substrate having a firstcoefficient of thermal expansion; a magnetic transducer coupled to thesubstrate, the magnetic transducer having a second coefficient ofthermal expansion that is greater than the first coefficient of thermalexpansion; a conductive layer coupled between the substrate and themagnetic transducer, the conductive layer having a third coefficient ofthermal expansion that is less than the first coefficient of thermalexpansion; and a non-magnetic layer coupled between the conductive layerand the magnetic transducer.
 2. The magnetic read/write head of claims1, wherein the conductive layer is a layer of plated Invar.
 3. Themagnetic read/write head of claims 2, wherein the plated Invar comprisesapproximately 34 to 38 percent Nickel and 62 to 66 percent Iron.
 4. Themagnetic read/write head of claims 2, wherein the plated Invar comprisesapproximately 0.1 to 5.0 percent of Cobalt, 35 to 36 percent of Nickel,and 62 to 64 percent of Iron.
 5. The magnetic read/write head of claims2, wherein the plated Invar is annealed at a temperature greater than450° C.
 6. The magnetic read/write head of claims 1, wherein theconductive layer coupled between the substrate and the magnetictransducer is between approximately 1.0 μm to 5.0 μm.
 7. The magneticread/write head of claims 1, wherein the conductive layer has theapproximate dimensions of a bottom shield of the magnetic transducer. 8.The magnetic read/write head of claims 1, wherein the non-magnetic layercoupled between the conductive layer and the magnetic transducercomprises at least one of tantalum and SiO₂.
 9. The magnetic read/writehead of claims 8, wherein the non-magnetic layer is betweenapproximately 0.1 μm and 1.0 μm.
 10. A method of forming a magneticread/write head, the method comprising: providing a substrate; plating aNiFe layer over the substrate; annealing the NiFe layer; depositing anon-magnetic layer over the NiFe layer; and producing a magnetictransducer over the non-magnetic layer.
 11. The method of claim 10,further comprising depositing an undercoating layer over the substrateprior to plating the NiFe layer.
 12. The method of claim 11, furthercomprising: removing a plating field of the NiFe layer; depositing acovering layer over the remaining NiFe layer and over the underlyingundercoating layer prior to annealing the NiFe layer; and polishing thecovering layer to expose the underlying NiFe layer.
 13. The method ofclaim 12, wherein the remaining NiFe layer has the approximatedimensions of a bottom shield of the magnetic transducer.
 14. The methodof claim 12, wherein the covering laying and the undercoating layercomprise alumina.
 15. The method of claim 10, wherein the NiFe layer isannealed above approximately 450 degrees C.
 16. The method of claim 15,wherein the NiFe layer is annealed at approximately 490 degrees C. forapproximately 2 hours.
 17. The method of claim 10, wherein the NiFelayer is plated at a ratio of approximately 34 to 38 percent Ni and 62to 66 percent Fe.
 18. The method of claim 10, wherein the NiFe layerfurther includes Co and is plated at a ratio of approximately 0.1 to 5.0percent of Co, 35 to 36 percent of Ni, and 62 to 64 percent of Fe. 19.The method of claim 10, wherein the NiFe layer is plated to a thicknessof approximately 1.0 μm to 5.0 μm.
 20. The method of claim 10, whereinthe non-magnetic layer comprises at least one of tantalum and SiO₂. 21.The method of claim 20, wherein the non-magnetic layer is deposited to athickness of approximately 0.1 μm to 1.0 μm.
 22. The method of claim 10,wherein the annealed NiFe layer has a coefficient of thermal expansionthat is less than the coefficient of thermal expansion of the substrate.23. A method of forming a magnetic read/write head, the methodcomprising: providing a substrate with a first coefficient of thermalexpansion; plating a conductive layer over the substrate; annealing theconductive layer, wherein the annealed conductive layer has a secondcoefficient of thermal expansion that is less than the first coefficientof thermal expansion; depositing a non-magnetic layer over theconductive layer; and fabricating a magnetic transducer over thenon-magnetic layer, wherein the magnetic transducer has a thirdcoefficient of thermal expansion that is greater than the firstcoefficient of thermal expansion.